This application claims the benefit of Korean Application No. 2002-43017, filed Jul. 22, 2002, Korean Application No. 2003-10809, filed Feb. 20, 2003, and Korean Application No. 2003-40666, filed Jul. 21, 2003, all filed in the Korean Intellectual Property Office, the disclosures of which are incorporated herein by reference.
1. Field of the Invention
The present invention relates to an image forming apparatus, and more particularly to an image forming apparatus that is readily redesignable for purposes such as an addition of an improvement or a new function, and a component arrangement method of the same.
2. Description of the Related Art
Image forming apparatuses such as laser printers receive print data from an image processing apparatus such as a personal computer and reproduce the received print data on a printing medium such as a paper sheet. Recently, such image forming apparatuses have been incorporated into a multi-functioned machine such as a fax-copier image forming apparatus.
As the image forming apparatus technology rapidly advances, the molding and the printed circuit board (PCB) are requiring more frequent updating. However, the metal molding by nature requires a longer time than the PCB for a design process, and also requires a reliability test after the design is completed. Accordingly, there is usually a three to five year interval until the image forming apparatus is redesigned, and usually, it is the PCB which is the subject of the redesign.
Meanwhile, due to individual characteristics, the design for the metal mold and the PCB are usually planned by separate companies. Thus, the metal mold generally needs to be equipped with various motors to drive the image forming apparatus and a PCB to control the motors. Usually, the motor and the PCB for motor control are available as a set, and when used to design the image forming apparatus, because the PCB has a verified quality, a reliability test time may be reduced. In contrast, if one buys the metal mold and PCB separately and attempts to design an image forming apparatus using them, since the user is also required to prepare and install components such as a random access memory and Flash ROM (or mask ROM, or EPROM) to store programs to drive the processor, the user would require a significant amount of time to complete the design.
FIG. 1 is a block diagram of an example of a conventional laser printer. The laser printer includes an image processing unit 20, a switching mode power supply (SMPS) 30, an engine controlling unit 40, a high voltage power supply (HVPS) 50 and an engine mechanism 60.
The image processing unit 20 converts the print data received from a host computer 10 into image data such as bit map data which are processible at the engine controlling unit 40. The SMPS 30 generates power for driving the image processing unit 20, the engine controlling unit 40, the HVPS 50 and the engine mechanism 60. The engine controlling unit 40 controls the driving of the engine mechanism 60 in accordance with the image data applied from the image processing unit 20. The engine mechanism 60 is driven by the engine controlling unit 40 to reproduce an image on the printing medium such as a paper, and includes necessary mechanical devices such as a motor, a roller and an organic photoconductor (OPC). The engine controlling unit 40 includes a processor (not shown), a random access memory (not shown) and a Flash ROM (or mask ROM, or EEPROM; not shown) to drive the processor. The engine controlling unit 40 controls the operation of the mechanical devices such as a motor, a roller and an OPC in response to the image data.
FIGS. 2A and 2B are block diagrams of the image processing unit 20 and the engine controlling unit 40 of FIG. 1. First, the image processing unit 20 of FIG. 2A includes an interface unit 21 which receives the print data from the host computer 10, a central processing unit (CPU) 23 to control the overall operation of the image processing unit 20, a ROM 22 to store various control programs and application programs for driving the CPU 22, a random access memory (RAM) 24 to temporarily store data generated during the print data processing, and an EEPROM 25 for storing initial conditions or control set values of the image processing unit 20.
The engine controlling unit 40 shown in FIG. 2B includes a ROM 41 to load control programs for the turn-on or resetting of the engine controlling unit 20 on the CPU 42, a CPU 42 to control the overall operation of the engine controlling unit 40 according to the programs stored in the ROM 41, a random access memory (RAM) 43 to temporarily store the data generated by the program execution of the CPU 42, an EEPROM 44 to store set values for setting control data or the operational states of the engine mechanism 60, and an engine interface unit 45 to provide interface between the engine mechanism 60 and the CPU 42.
As described above, conventionally, the engine controlling unit 40 and the image processing unit 20 were formed on separate PCBs, each of which being equipped with the processor 23, 42, the ROM 22, 41, the random access memory 24, 43 and the EEPROM 25, 44. Accordingly, a separate interface (not shown) was required for the data transmission between the processors 23, 42 of the two separate PCBs. For example, for the processors 23, 42 to support different input/output interfaces, an interface circuit is inevitably required to convert two different data formats of the processors 23, 42. The requirement for the extra parts such as an interface circuit increases the unit price of the image forming apparatus, while degrading the data transmission speed between the processors 23, 43.
FIG. 3 is a schematic sectional view illustrating the engine mechanism 60 of FIG. 1. The engine mechanism 60 includes a photosensitive drum 61 having an electrically-chargeable layer to facilitate formation of an electric potential difference at the area charged by the exposure to the light of the light source, a laser scanning unit (LSU) 63 which converts the image data into optical signals, irradiates the optical signals onto the photosensitive drum 61 to form an electrostatic latent image by the electric potential difference, a developing unit 64 which sequentially supplies toners of respective colors onto the photosensitive drum 61, a transfer unit 65 which transfers the toner image from the photosensitive drum 61 onto a printing paper P, and a fusing unit 66 which fixes the transferred toner image on the printing paper P.
The developing unit 64 includes four toner reservoirs 64axcx9c64d that sequentially feed toners of respective colors such as yellow Y, magenta M, cyan C and black B to develop the image on the photosensitive drum 61. The reference numeral 64e denotes a developing roller which applies yellow color toner onto the photosensitive drum 61. Although not shown, the developing roller is also provided to the other toner reservoirs 64bxcx9c64d. 
The transfer unit 65 includes a transfer belt 65a that serves as a transfer medium for the toner image of the photosensitive drum 61, a first transfer roller 65b which transfers the toner image of the photosensitive drum 61 onto the transfer belt 65a, and a second transfer roller 65c which transfers the toner image of the transfer belt 65a onto the printing paper P.
The image forming apparatus, constructed as above, forms a desired electrostatic latent image on the photosensitive drum 61 as the laser beam is irradiated from the LSU 63 onto certain areas of the photosensitive drum 61 that is charged to a predetermined potential by the charging unit 62.
Next, the electrostatic latent image is developed by the developing unit 64, in which usually the yellow Y, magenta M, cyan C and black B toners of the toner reservoirs 64axcx9c64d are sequentially fed onto the photosensitive drum 61 by the rotation of the developing unit 64.
Each color toner image, which has been developed on the photosensitive drum 61 by the developing process above, is overlappingly transferred onto the transfer belt 65a, and the image formed on the transfer belt 65a by the color toner images is then transferred onto the printing paper P, wherein the image is transferred from the transfer belt 65a using the second transfer roller 65c. 
The printing paper P bearing the image thereon is passed through the fusing unit 66, where the image is fixed on the printing paper P. Then the printing paper P is discharged.
FIG. 4 shows the arrangement of the harness in the image forming apparatus including the image processing unit 20, the engine controlling unit 40 and the engine unit 60 of FIGS. 1 to 3. As shown in FIG. 4, a harness guide 70 is arranged along the boundary of the PCBs 20a, 40a of the image processing unit 20 and the engine controlling unit 40 to protect the electric lines and signal lines for the components of the engine mechanism 60, i.e., the photosensitive drum 61, the charging unit 62, the LSU 63, the developing unit 64, the transfer, unit 65 and the fusing unit 66. The PCBs 20a, 40a are respectively designed and arranged for the image processing unit 20 and the engine controlling unit 40, for the convenience of upgrading and designing. Each of the PCBs 20a, 40a is equipped with a central processing unit (CPU), a random access memory (RAM) and a read only memory (ROM).
As described above, the image processing unit 20 and the engine controlling unit 40 are formed on the separate PCBs 20a, 40a, each with the CPU, RAM, ROM and EEPROM. By this structure, when there is a need to add or upgrade a certain function such as a resolution/printing speed increase or a copy/fax function, adding the function to the image forming apparatus such as a laser printer is non-complex because only the PCB mounted with the image processing unit 20 may be replaced. However, in order to add or upgrade a function, because the image processing unit 20 and the engine controlling unit 40 need to be re-mounted on the separate PCBs, each having the CPU, RAM and ROM, the manufacturing cost of the image forming apparatus increases. Further, in the case of upgrading the engine controlling unit 40, the image processing unit 20 is accordingly upgraded because the image processing unit 20 interfaces with the engine controlling unit 40. Accordingly, after the redesign is completed, both the engine controlling unit 40 and the image processing unit 20 have to undergo a reliability test on the PCBs 20a, 40a thereof, and then additionally through the EMI tests. As a result, the redesign process and the costs increase. Further, each of the engine controlling unit 40 and the image processing unit 20 have independent processors 42, 23, which are required to be connected through a separate interface circuit (not shown). Of course, a low-speed serial bus may be utilized for the simple information exchange such as a simple control command or status information. However, the control signals from the image processing unit 20 to the printing engine unit have to be transmitted at high speed. Thus, for the color image forming apparatus, a high transmission speed of the printing control data and printing data facilitates efficient printing.
Additional aspects and/or advantages of the invention will be set forth in part in the description which follows and, in part, will be obvious from the description, or may be learned by practice of the invention.
Accordingly, it is an aspect of the present invention to provide a PCT design method to reduce time and cost for the redesign of an image forming apparatus when there is need to improve printing performance or add a new function, and an image forming apparatus thereof.
It is another aspect of the present invention to provide an image forming apparatus to increase data transmission speed between the engine controlling unit and the image processing unit, and a method to mount the image forming apparatus on the PCB.
To achieve the above aspects and/or other features in an embodiment of the present invention, an image forming apparatus includes an engine mechanism to carry out a printing job with respect to a print data, an image processing unit to convert the print data into image data recognizable by the engine mechanism, and an engine controlling unit to control the engine mechanism to carry out the print job with respect to the image data. The engine controlling unit and the image processing unit are arranged on a single printed circuit board (PCB) in which a first division and a second division are defined, with the engine controlling unit being arranged in the first division and the image processing unit being arranged in the second division, wherein a circuit element in the second division is shared by the engine controlling unit and the image processing unit.
In an aspect, the image processing unit and the engine controlling unit are connected via a bidirectional parallel bus.
In another aspect, the image processing unit has a single processor, and the engine controlling unit is driven by the control of the single processor.
In an aspect, the engine controlling unit is configured as an application specific integrated circuit (ASIC).
In another aspect, the processor and the ASIC are arranged to face each other.
In an aspect, the engine controlling unit comprises at least one connector to interface with the engine mechanism, the connector being arranged to face a connection pin of the ASIC in a perpendicular and a horizontal relation.
In another aspect, the shared circuit element comprises at least one of a random access memory (RAM), a Flash read only memory (ROM) and a read only memory (ROM).
In an aspect, the engine controlling unit shares at least one of the RAM, the Flash ROM and the ROM with the image processing unit.
In another aspect, the image processing unit further comprises a connector to receive the print data, the connector being arranged to face a connection pin of the image processing unit in a perpendicular and a horizontal relation.
According to an embodiment of the present invention, an image forming apparatus includes an engine mechanism to carry out a print job with respect to a print data, an image processing unit to convert the print data into image data recognizable by the engine mechanism, and an engine controlling unit to control the engine mechanism to carry out the print job with respect to the image data. The image processing unit and the engine controlling unit are each configured as a processor and an application specific integrated circuit (ASIC), which are directly connected via a bidirectional bus.
In an aspect, the ASIC generates a control signal to drive the engine mechanism in response to the image data applied from the image processing unit.
In another aspect, the ASIC further comprises a memory to store status information of the engine mechanism.
In an aspect, the processor checks the status of the engine mechanism by reading the stored status information from the memory, and controlling the ASIC to transmit the image data to the engine controlling unit and carry out the print job.
In another aspect, the bidirectional bus comprises at least one an address bus, a data bus and a control bus, and configured as a parallel bus.
In an aspect, the processor and the ASIC are directly connected with each other via the bidirectional bus, and are arranged to face each other.
In another aspect, the image processing unit and the engine controlling unit are arranged on a single printed circuit board (PCB) which has more than one division defined thereon, and are directly connected with each other via the bidirectional bus.
In an aspect, the engine controlling unit comprises at least one connector to connect to the engine mechanism, and the connector is arranged to face a connection pin of the ASIC in a horizontal and a perpendicular relation.
According to an embodiment of the present invention, a PCB arrangement method of an image forming apparatus includes an arrangement of an engine mechanism to carry out a print job with respect to print data applied from an external device, an image processing unit to convert the print data from the external device into image data format, and an engine controlling unit to control the engine mechanism to carry out the print job with respect to the image data. The PCB arrangement method arranges the image forming apparatus on a single PCB, and includes the operations of defining the PCB into a first and a second division, and arranging the image process in the first division and the engine controlling unit in the second division, in a manner that the image processing unit and the engine controlling unit share a circuit element which is arranged in the first division.
In an aspect, the operation of arrangement in the first division further comprises the operation of installing a connector in the first division to interface with the engine mechanism.
In another aspect, the connector is arranged in at least a part of a boundary of the PCB corresponding to the first division.
In an aspect, the shared circuit element comprises at least one of a random access memory (RAM), a Flash read only memory (ROM) and a read only memory (ROM).
In another aspect, the engine controlling unit shares at least one of the RAM, the Flash ROM and the ROM with the image processing unit.
In an aspect, The image processing unit is arranged in the second division and has a connector to interface with the external device, the connector being arranged to face the image processing unit.
Additionally, according to an embodiment of the present invention, a PCB arrangement method of an image forming apparatus includes an arrangement of an engine mechanism to carry out a print job with respect to print data applied from an external device, an image processing unit to convert the print data from the external device into image data format, and an engine controlling unit to control the engine mechanism to carry out the print job with respect to the image data. The PCB arrangement method according to an embodiment of the present invention includes the operations of arranging the image processing unit and the engine controlling unit on a single PCB, and connecting the image processing unit and the engine controlling unit on the single PCB via a bidirectional parallel bus.
In an aspect, the image processing unit is configured as a processor and the engine controlling unit is configured as an application specific integrated circuit (ASIC).
In another aspect, the image processing unit and the engine controlling unit are arranged to face each other.
In an aspect, the method further includes the operation of installing a connector to a side of the single PCB to interface between the engine controlling unit and the engine mechanism.